This invention relates generally to a comparison circuit for comparing input signals to a reference potential and more particularly to a comparison circuit having bidirectional hysteresis.
Many forms of comparison circuits are generally known in the art for comparing an input signal to a reference signal to produce an output signal indicative of some predetermined relationship therebetween. Generally, these comparison circuits comprise a differential amplifier circuit wherein a reference potential is applied at one input thereof and an input signal is applied to the other input. A particular kind of load circuitry is connected to the differential amplifier circuit for producing the output signal when the input signal obtains a predetermined relationship with respect to the reference signal. For example, U.S. Pat. No. 3,872,323 to Thomas M. Frederiksen et al, issued Mar. 18, 1975 discloses a comparision circuit comprising such a differential amplifier and a differential to single ended converter circuit which is exemplary of the prior art.
Whenever such comparision circuits are used in a high noise environment there is always a chance that the comparator circuit may be falsely tripped by generated noise. Therefore, it is desirable to introduce hysteresis into the comparator circuit such that after the input signal has reached a predetermined magnitude the comparator circuit will be tripped and thereafter is not affected by any high noise generated on the input signal. Comparison circuits having hysteresis introduced therein are generally known in the art as exemplified by U.S. Pat. No. 3,725,673 issued Apr. 3, 1973 to Thomas M. Frederiksen.
A problem with many of the prior art comparison circuits having hysteresis introduced therein is the complexity of the circuitry required to provide the hysteresis. A need therefore exists in the art to provide a comparision circuit generally free of complexity in its circuitry and therefore inexpensive to fabricate.